As the British government edged towards committing troops to Iraq, a human rights lawyer joined a million people on the streets of London in 2003 in an effort to block the path to war. Keir Starmer, who had a growing reputation for taking on cases against states and corporations, backed up his protest with a measured legal opinion published in a national newspaper that the coming war would be illegal. His ultimately unsuccessful efforts to prevent British troops heading to the Middle East were nonetheless a key moment in the political rise of the former hard-left activist. Seventeen years after the protest – and only five after becoming an MP – he now will be able to put his human rights-based internationalism into effect as the new leader of the UK’s main opposition Labour party. The 57-year-old won on the first round of voting with 56.2 per cent of all the votes cast on Saturday, putting him well ahead of rivals Rebecca Long-Bailey and Lisa Nandy. Despite his comfortable win to become Labour leader, Mr Starmer now has more immediate problems of re-invigorating a party that last won an election in 2005 and was crushed at the polls by Boris Johnson’s right-of-centre Conservative Party in December. Angela Rayner was chosen on Saturday as deputy leader in a vote of Labour’s half a million members. Although she ran a low key campaign, Ms Rayner emerged as the clear frontrunner through all the rounds of voting, winning 52.6 per cent of the vote on the final round and succeeding Tom Watson. Despite Mr Johnson flying high in public opinion polls after securing his immediate goal of leaving the European Union, the combined threats of coronavirus and Brexit have the potential to destabilise the unpredictable prime minister and place in Mr Starmer in pole position to become the next UK leader in 2024. His first task is to make the party electable again. Labour last topped the polls in 2005 in the final years of Tony Blair’s decade-long premiership and that of his short-lived successor Gordon Brown. Many in his party see Mr Starmer as a stop-gap choice whose time will end at elections in 2024 after efforts to reunite a party wracked by division after four chaotic years with veteran left-winger Jeremy Corbyn as its leader. The historic scale of the defeat, the worst for the party since the 1930s, was in large part attributed to the party’s disarray over Brexit. Mr Starmer held the party’s Brexit portfolio but emerged with his reputation enhanced after being forced to juggle the competing wings of pro-European younger supporters and disaffected traditional members. But Mr Starmer’s record as both prominent lawyer and politician raises key questions about how – and if – he will bring the powerful left-wing to heel and what his policies will mean if Britain regains its status as an influential global nation. His ten election pledges to party members who elected him includeded one to “peace and human rights”. “No more illegal wars,” it said in an obvious reference to Mr Blair’s decision to take Britain to war in 2003, a move that has dominated discussion of his legacy. He has promised to review all British arms sales and to create a new Prevention of Military Intervention Act’ that would “put human rights at the heart of foreign policy.” The statement was criticised by some supporters on the left, who applauded the decision by Mr Blair to lead humanitarian interventions to protect Bosnian Muslims in 1999 and in Sierra Leone. “I’m all for gesture politics, but this is spineless,” said prominent political commentator John Rentoul. “At least call it ‘Abandon Sierra Leoneans, Kosovars, and Kurds Act’.” Mr Starmer – who also opposed airstrikes against ISIS in 2015 in line with his party’s policy - later told the BBC that the commitment meant that Britain would only go to war if there was a lawful case, a viable objective and the consent of MPs in parliament. “We have to be questioning as to how swiftly we turn to military options before we exhaust all the diplomatic and political ones,” said Clive Efford, a Labour MP and a Starmer backer. Mr Starmer has signalled that under his premiership, Labour would end arms sales to Saudi Arabia because of humanitarian suffering in Yemen, a manifesto pledge at the December 2019 elections. He is also a critic of US President Donald Trump’s maximum pressure campaign – in line with the policy of other European countries that are seeking to continue with the 2015 nuclear deal. “The international community needs to re-engage, not isolate Iran,” Mr Starmer wrote after the killing of Qassem Suleimani in January. “The nuclear deal agreed after years of painstaking diplomacy shows that a different approach is possible.” But Prof Malcolm Chalmers, of London-based think tank the Royal United Services Institute, said foreign affairs issues had not featured much in the leadship campaign. "He does seem to be especially focused on international law, unsurprising given his background, and this may be especially relevant in discussions on UK military interventions," he said. Mr Corbyn, the outgoing leader, had faced questions during his tenure as leader about his activities while a backbench MP when he described Hamas and Hezbollah as friends. He later said he used the word as a collective term for those trying to resolve the Palestinian issue. He also received money for appearances on Iranian state broadcast network Press TV between 2009 and 2012. Mike Gapes, a former long-serving Labour MP and chair of the foreign affairs committee, said it was unclear if Labour would continue under Mr Starmer with its “myopic one-eyed view of the world – soft on Iran and hostile to Saudi Arabia”. Mr Starmer – named after one of the founders of the Labour Party Keir Hardie by his left-wing parents – said in his election campaign that he embraced causes defending the powerless during his legal career. He campaigned to end the death penalty in the Caribbean and acted on behalf of a British-Iraqi suspected terrorist held by British troops in Iraq. He defended striking workers and environmental activists against police officers. He also headed legal action against the last Labour government over its decision to deny welfare benefits to asylum seekers. Given his position as scourge of the state, he was a surprise pick by Labour leader Gordon Brown in 2009 to become the head of the body with responsibility for prosecutions in the criminal courts of England and Wales. His most difficult decision, he later said on stepping down in 2013, was over the prosecution of a police officer, accused of killing a newspaper seller who had got caught up in demonstrations against a meeting of the G20 group of nations in the UK. The prosecution agency initially decided not to prosecute the officer only to reverse the decision. The officer was later acquitted at trial but with enough question marks over his conduct for one newspaper to run a headline reading: “Not guilty. But no innocent”. Mr Starmer announced charges against politicians for fiddling their expenses – some were put behind bars – and for journalists accused of hacking telephones, who mostly weren’t. After quitting in 2013, the rise of the telegenic, smooth-talking lawyer through the political ranks was rapid to hold the complex Brexit post. He is seen as the potential saviour of a bitterly-divided party from its right-wing and his message of unity – he is pictured hugging Mr Corbyn in his campaign video – has appealed to some on the left. But the Sunday Times reported last week that Mr Starmer was planning a purge on Mr Corbyn’s allies and party loyalists. “It’s a step back towards reality and soon than I anticipated,” said Simon Danczuk, a former MP who quit the party in 2017 in protest at Mr Corbyn’s policies. “Success in the short-term is him having a clear out and getting rid of some of the far-left shadow cabinet members. It’s crucial. Others are less convinced that he has the powers to reunite the party. Mr Gapes says he lacks political courage and the “strategic big picture view of Blair”. But he said that a looming report on anti-Semitism that is likely to be highly critical of party officials could give him the opportunity to fire some of those that oppose his planned reforms. Mr Efford said the government’s response to the coronavirus crisis, which has been criticised for failing to join a European ventilator-sourcing programme, has highlighted what Mr Starmer could bring as leader of the country at the next elections in 2024. “We have to re-establish ourselves as a major player in the world and as a country that’s’ still prepared to play its part taking responsibilities in international incidents,” he said. “That’s what’s lacking at the moment.”